Create Authors yaml key, list and ui

[thanpolas]

create a key for yaml front matter on posts author which will accept a value from a separate yaml file that will contain the author's data (name, email, website, twitter ...)

Then present the data to the post.

yaml front matter on post:

----
-author: rhys
----

yaml file with authors:

authors:
  rhys:
    name : "Rhys Brett-Bowen"
    email : ""
    github : rhysbrettbowen
    twitter : rhysbb